Inhibition of de novo pyrimidine synthesis augments Gemcitabine induced growth inhibition in an immunocompetent model of pancreatic cancer

Leflunomide (Lef) is an agent used in autoimmune disorders that interferes with DNA synthesis. De Novo pyrimidine synthesis is a mechanism of Gemcitabine (Gem) resistance in pancreatic cancer. This study aims to assess the efficacy and changes in the tumor microenvironment of Lef monotherapy and in combination with Gem, in a syngeneic mouse model of pancreatic cancer. Methods: MTS proliferation assays were conducted to assess growth inhibition by Gem (0-20 nM), Lef (0-40 uM) and Gem+Lef in KPC (KrasLSL.G12D/+;p53R172H/+; PdxCretg/+) cells in vitro. An in vivo heterotopic KPC model was used and cohorts were treated with: PBS (control), Gem (75 mg/kg/q3d), Lef (40 mg/kg/d), or Gem+Lef. At d28 post-treatment, tumor burden, proliferation index (Ki67), and vascularity (CD31) were measured. Changes in the frequency of peripheral and intratumoral immune cell subsets were evaluated via FACS. Liquid chromatography-mass spectrometry was used for metabolomics profiling. Results: Lef inhibits KPC cell growth and synergizes with Gem in vitro (P<0.05; Combination Index 0.44 (<1 indicates synergy). In vivo, Lef alone and in combination with Gem delays KPC tumor progression (P<0.001). CTLA-4+T cells are also significantly decreased in tumors treated with Lef, Gem or in combination (Gem+Lef) compared to controls (P<0.05). Combination therapy also decreased the Ki67 and vascularity (P<0.01). Leflunomide inhibits de novo pyrimidine synthesis both in vitro (p<0.0001) and in vivo (p<0.05). Conclusions: In this study, we demonstrated that Gem+Lef inhibits pancreatic cancer growth, decrease T cell exhaustion, vascularity and as proof of principle inhibits de novo pyrimidine synthesis. Further characterization of changes in adaptive immunity are necessary to characterize the mechanism of tumor growth inhibition and facilitate translation to a clinical trial.

Development of a multi-antigenic SARS-CoV-2 vaccine candidate using a synthetic poxvirus platform

Modified Vaccinia Ankara (MVA) is a highly attenuated poxvirus vector that is widely used to develop vaccines for infectious diseases and cancer. We demonstrate the construction of a vaccine platform based on a unique three-plasmid system to efficiently generate recombinant MVA vectors from chemically synthesized DNA. In response to the ongoing global pandemic caused by SARS coronavirus-2 (SARS-CoV-2), we use this vaccine platform to rapidly produce fully synthetic MVA (sMVA) vectors co-expressing SARS-CoV-2 spike and nucleocapsid antigens, two immunodominant antigens implicated in protective immunity. We show that mice immunized with these sMVA vectors develop robust SARS-CoV-2 antigen-specific humoral and cellular immune responses, including potent neutralizing antibodies. These results demonstrate the potential of a vaccine platform based on synthetic DNA to efficiently generate recombinant MVA vectors and to rapidly develop a multi-antigenic poxvirus-based SARS-CoV-2 vaccine candidate.

Development of a Multi-Antigenic SARS-CoV-2 Vaccine Using a Synthetic Poxvirus Platform

Modified Vaccinia Ankara (MVA) is a highly attenuated poxvirus vector that is widely used to develop vaccines for infectious diseases and cancer. We developed a novel vaccine platform based on a unique three-plasmid system to efficiently generate recombinant MVA vectors from chemically synthesized DNA. In response to the ongoing global pandemic caused by SARS coronavirus-2 (SARS-CoV-2), we used this novel vaccine platform to rapidly produce fully synthetic MVA (sMVA) vectors co-expressing SARS-CoV-2 spike and nucleocapsid antigens, two immunodominant antigens implicated in protective immunity. Mice immunized with these sMVA vectors developed robust SARS-CoV-2 antigen-specific humoral and cellular immune responses, including potent neutralizing antibodies. These results demonstrate the potential of a novel vaccine platform based on synthetic DNA to efficiently generate recombinant MVA vectors and to rapidly develop a multi-antigenic poxvirus-based SARS-CoV-2 vaccine candidate.

Development of a Synthetic Poxvirus-Based SARS-CoV-2 Vaccine

Modified Vaccinia Ankara (MVA) is a highly attenuated poxvirus vector that is widely used to develop vaccines for infectious diseases and cancer. We developed a novel vaccine platform based on a unique three-plasmid system to efficiently generate recombinant MVA vectors from chemically synthesized DNA. In response to the ongoing global pandemic caused by SARS coronavirus-2 (SARS-CoV-2), we used this novel vaccine platform to rapidly produce fully synthetic MVA (sMVA) vectors co-expressing SARS-CoV-2 spike and nucleocapsid antigens, two immunodominant antigens implicated in protective immunity. Mice immunized with these sMVA vectors developed robust SARS-CoV-2 antigen-specific humoral and cellular immune responses, including potent neutralizing antibodies. These results demonstrate the potential of a novel vaccine platform based on synthetic DNA to efficiently generate recombinant MVA vectors and to rapidly develop a multi-antigenic poxvirus-based SARS-CoV-2 vaccine candidate.

Abstract 2111: Role of gene repression by estrogen in invasiveness of breast cancer cells

More than 75% of breast tumors are estrogen receptor (ER)-positive and require estrogen for their growth and survival. Long-term adjuvant therapies that disrupt estrogen signaling, in particular tamoxifen and aromatase inhibitors, are a mainstay in breast cancer treatment. The principal focus of mechanistic studies evaluating the role of estrogen in breast cancer proliferation has been on gene activation by estrogen and its antagonism by anti-estrogens. Gene repression by estrogen and its antagonism by anti-estrogens have unclear physiological and therapeutic consequence in breast cancer. In this study, we found that estrogen-repressed genes but not estrogen-activated genes overlapped the gene overexpression signature of clinical progression of ductal carcinoma in situ to invasive ductal carcinoma. An extensive gene ontology analysis revealed that genes repressed by estrogen are enriched for functions known to collectively support breast cancer progression. In ER-positive breast cancer cells tamoxifen prevented gene repression by estrogen. In these cells, estrogen inhibited invasiveness in a manner that was opposed by tamoxifen. These effects of estrogen and tamoxifen on gene repression and invasiveness also occurred in Her2+/ER+ cells whose growth was hormone-independent and insensitive to tamoxifen. The effects were also independent of ErbB2 gene regulation by estrogen. Several ER co-repressors supported repression of the tumor progression genes by estrogen. Gene repression by estrogen was causally linked to inhibition of invasiveness as a co-repressor binding site mutation in ER that selectively disrupted the ability of estrogen to repress genes also prevented inhibition of invasiveness. Gene repression by estrogen involved ER binding at non-classical chromatin sites that was prevented by tamoxifen. The findings offer a mechanistic understanding of the invasive potential of ER+ breast cancer cells that have evaded growth inhibition during conventional anti-estrogen treatments.

Citation Format: Mugdha Patki, Marcela d'Alincourt Salazar, Robert Trumbly, Manohar Ratnam. Role of gene repression by estrogen in invasiveness of breast cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2111. doi:10.1158/1538-7445.AM2014-2111

Hormone depletion-insensitivity of prostate cancer cells is supported by the AR without binding to classical response elements

A need for androgen response elements (AREs) for androgen receptor (AR)-dependent growth of hormone depletion-insensitive prostate cancer is generally presumed. In such cells, androgen-independent activation by AR of certain genes has been attributed to selective increases in basal associations of AR with putative enhancers. We examined the importance of AR binding to DNA in prostate cancer cells in which proliferation in the absence of hormone was profoundly (∼ 90%) dependent on endogenous AR and where the receptor was not up-regulated or mutated but was predominantly nuclear. Here, ARE-mediated promoter activation and the binding of AR to a known ARE in the chromatin remained entirely androgen dependent, and the cells showed an androgen-responsive gene expression profile with an unaltered sensitivity to androgen dose. In the same cells, a different set of genes primarily enriched for cell division functions was activated by AR independently of hormone and significantly overlapped the signature gene overexpression profile of hormone ablation-insensitive clinical tumors. After knockdown of endogenous AR, hormone depletion-insensitive cell proliferation and AR apoprotein-dependent gene expression were rescued by an AR mutant that was unable to bind to ARE but that could transactivate through a well-established AR tethering protein. Hormone depletion-insensitive AR binding sites in the chromatin were functional, binding, and responding to both the wild-type and the mutant AR and lacked enrichment for canonical or noncanonical ARE half-sites. Therefore, a potentially diverse set of ARE-independent mechanisms of AR interactions with target genes must underlie truly hormone depletion-insensitive gene regulation and proliferation in prostate cancer.

C/EBPalpha redirects androgen receptor signaling through a unique bimodal interaction

Nuclear expression of CCAAT enhancer binding protein-alpha (C/EBPalpha), which supports tissue differentiation through several antiproliferative protein-protein interactions, augurs terminal differentiation of prostate epithelial cells. C/EBPalpha is also a tumor suppressor, but in many tumors its antiproliferative interactions may be attenuated by de-phosphorylation. C/EBPalpha acts as a corepressor of the classical androgen response element (ARE)-mediated gene activation by the androgen receptor (AR), but this is paradoxical as the genotropic actions of AR are crucial not only for the growth of the prostate but also for its maintenance and function. We show that DNA-bound C/EPBalpha recruits AR to activate transcription. C/EBPalpha-dependent trans-activation by AR also overrode suppression of AREs by C/EBPalpha elsewhere in a promoter. This mechanism was remarkable in that its androgen dependence was apparently for nuclear translocation of AR; it was otherwise androgen independent, flutamide insensitive and tolerant to disruption of AR dimerization. Gene response profiles and global chromatin associations in situ supported the direct bimodal regulation of AR transcriptional signaling by C/EBPalpha. This unique mechanism explains the functional coordination between AR and C/EPBalpha in the prostate and also shows that hormone-refractory AR signaling in prostate cancer could occur through receptor tethering.

[Cross-sectional study of intestinal parasites and Chagas' disease in the Municipality of Novo Airão, State of Amazonas, Brazil]

A cross-sectional study was performed on the residents of one in every ten households in the town of Novo Airão, in the northern meso-region of the State of Amazonas, 250 kilometers from Manaus by riverboat. A family cluster sample of 89 dwellings was studied. A stool sample was requested from each of the inhabitants for examination using the Lutz sedimentation and Baermann-Moraes-Coutinho techniques, and blood was taken by venous puncture for Trypanosoma cruzi Elisa antibody testing and immunofluorescence. From a total of 316 stool samples, 87.6% had one or more parasites: Ascaris lumbricoides (35.1%), Entamoeba histolytica (29.1%), Giardia lamblia (17.4%), and other parasites with lower prevalence rates. These results were directly correlated with lack of sanitation and clean water supply. Of the 346 sera examined, 16 (4.6%) were reactive to T. cruzi antibodies, but only three showed a correlation between this result and human contact with wild triatomines, known locally as "piassava lice".